The instant invention relates to motorized vehicles and more particularly to a novel chassis and suspension system which provides optimal high speed handling characteristics in a motorized vehicle, particularly a racing type vehicle.
A wide variety of suspension systems have heretofore been available and have been adapted to achieve various handling characteristics in different types of vehicles. However, virtually all of the heretofore known suspension systems have involved certain design compromises, wherein certain handling and/or ride characteristics have been sacrificed in order to achieve certain other characteristics which have been considered more important for the particular vehicle. For example, many of the typical passenger vehicles currently in use are designed for economy and smooth ride but handle relatively poorly in high speed cornering situations. Some of the more expensive specialty passenger vehicles utilize more sophisticated and expensive suspension systems to achieve improved handling characteristics but even these systems are generally deficient in one or more areas. Typical racing vehicles frequently utilize independent suspension systems comprising independent A-arms or wishbone-arms and extremely stiff springs to achieve improved handling characteristics but they generally provide extremely harsh ride characteristics which can result in driver fatigue.
One factor which has proven to be of primary importance in achieving good handling characteristics in a vehicle under high speed cornering situations is the tire adhesion of the vehicle which is directly related to the resistance of the vehicle to lateral slip during cornering. In this connection, the tire adhesion of a vehicle depends both on the design of the vehicle tires per se and on the design of the vehicle, particularly the suspension system thereof. It has been found that the contact area between the tires of a vehicle and the road surface, commonly referred to as the contact patch area, is of particular significance and should generally be maximized in order to maximize the tire adhesion of the vehicle during cornering situations. Specifically, this is because when the contact patch area of a tire is increased, there is a greater tire area to absorb the centripetal forces acting thereon during cornering situations and hence, the tire is deformed to a lesser degree. As a result, the tire can absorb greater lateral or centripetal forces before it is deformed to the point where it looses adhesion.
The size of the contact patch area of a tire during cornering is influenced both by the size and quality of the tire as well as by the handling characteristics of the vehicle on which it is mounted. Substantial improvements have been realized in recent years in tire design and have resulted in improved tire adhesion characteristics for virtually all high speed vehicles. With regard to vehicle design, it has been found that it is advantageous to maintain the wheels and tires of a vehicle in substantially perpendicular relation to a roadway surface at all times, and particularly during cornering of the vehicle, to maximize contact patch area and thereby achieve optimum tire adhesion. In this connection, the degree of wheel or tire camber, which is the degree of deviation of the wheel or tire from perpendicular relation to a roadway surface is, therefore, a primary concern in the design of a high speed vehicle. Specifically, wheel or tire camber should be maintained at nearly zero in order to maximize tire contact patch area and hence tire adhesion. For example, it has been found that an increase in the camber of the wheels or tires of a vehicle by as little as one half of a degree can drastically reduce the overall contact patch area of the vehicle tires and thereby significantly reduce the ability of the vehicle to resist "spinout". However, while the benefits of maintaining the wheels of a vehicle in zero camber dispositions have been recognized, the heretofore available suspension systems have not been able to effectively achieve this.
Another important consideration in the design of a high speed vehicle is the ability of the vehicle to encounter bumps without causing the tires of the vehicle to lose roadway adhesion. Most high speed vehicles utilize independent suspension systems wherein the individual wheels of the vehicle are independently suspended and yield independently when bumps are encountered. Independent springs and dampers are provided to dampen the uplift effects on the individual wheels.
It has also been found to be desirable to minimize the "unsprung weight" of a vehicle to enhance the ability of the vehicle to absorb bumps. In this regard, the term, "unsprung weight", relates to the portions of a vehicle, such as the wheels and tires thereof, which normally yield upwardly when bumps are encountered, as opposed to the chassis, engine, driver, fuel, water, etc. which comprise the "sprung weight" of the vehicle and which remain substantially stationary under such conditions. The ratio between the "unsprung weight" and the "sprung weight" of a vehicle has proven to be a useful parameter in determining proper spring and dampening rates in vehicle suspension designs. In this regard, the "unsprung weight" of a vehicle is directly related to the amount of upward momemtum which is imparted to the vehicle when a bump is encountered. Therefore, by minimizing the "unsprung weight" of the vehicle, the momentum imparted thereto by a pump can be minimized to minimize the effect of the bump.
The instant invention provides a novel independent suspension system, wherein the wheels of a vehicle are maintained in substantially zero camber dispositions under virtually all conditions. Accordingly, the vehicle wheels are maintained substantially perpendicular to a roadway surface therebeneath even under severe cornering conditions, so that overall contact patch area of the vehicle is maximized. The suspension system of the instant invention is also suited for light "unsprung weight" designs to minimize the momentum imparted to the wheels of a vehicle when bumps are encountered. When embodied in a high speed racing type vehicle, the chassis and suspension system can be constructed with substantially softer springs than currently used in conventional racing vehicles so that driver fatigue can be minimized. In addition, because the unique chassis and suspension system of the instant invention maintains the wheels of a vehicle in substantially zero camber dispositions, the suspension system is particularly adapted for use in combination with aerodynamic venturi ducts which draw a vehicle downwardly to increase the downward forces on the tires thereof to thereby further enhance the tire adhesion characteristics. Specifically, the suspension system of the instant invention includes front and rear subchassis which are maintained in substantially level dispositions at all times. As a result, by mounting the venturi ducts on the front and rear subchassis, the ducts also remain level under all conditions, including cornering conditions. Consequently, the venturi ducts of the vehicle can be mounted so that they are maintained in relatively closely spaced relation to a roadway surface without engaging same as a result of swaying during cornering.
The chassis and suspension system of the instant invention comprises a chassis, a front subchassis, a rear subchassis, right and left front wheels, and right and left rear wheels. Front connecting means rotatably mount the right and left front wheels so that they are resiliently upwardly movable on the right and left sides of the front subchassis, respectively, for supporting same on a supporting surface, the front wheels being pivotable to effect steering of the vehicle, and rear connecting means rotatably mount the right and left rear wheels so that they are resiliently upwardly movable on the right and left sides of the rear subchassis, respectively, for supporting the rear subchassis on the supporting surface. Means are also provided for pivotally suspending the front and rear portions of the chassis from the front and rear subchassis, respectively, so that the chassis is pivotable about a substantially longitudinal axis in the vehicle which is above the longitudinal center of gravity axis of the chassis, and means are provided for independently resiliently interconnecting the front and rear portions of the chassis to the front and rear subchassis, respectively, to resiliently restrict the pivotal movement of the chassis relative to the front and rear subchassis.
As a result of the pivotal interconnection between the chassis and the front and rear subchassis, when a vehicle embodying the chassis and suspension system of the instant invention moves in an arcuate path on a supporting surface, equal and opposite moments are applied by the chassis and the two subchassis about the pivot axis. The moment applied by the chassis can be computed from the vertical distance between the longitudinal center of gravity axis of the chassis and the pivot axis and the centrifugal forces on the chassis as they are applied along the longitudinal chassis center of gravity axis. The moments applied by the two subchassis can be computed from the centripetal forces applied to the subchassis by the roadway surface as translated through the wheels and the suspension arms, and the heights of the axles, the heights of suspension arms, and the height of the pivot axis. Because the chassis is pivotable about the pivot axis, when equilibrium conditions are reached during vehicle cornering, the chassis will normally be pivoted to a certain degree relative to the subchassis, and the chassis and/or the subchassis will also be pivoted relative to the roadway surface. However, by properly dimensioning the chassis, the wheels, and the two subchassis, by properly adjusting the positions of the suspension arms, and by selecting the proper resiliency for the means resiliently interconnecting the two subchassis to the chassis as by using trial and error techniques and/or known mathematical calculation techniques, it is possible to "tune" the chassis and suspension system of the instant invention so that when equilibrium conditions are reached during cornering, only the chassis assumes a rotated disposition relative to the roadway surface and the two subchassis remain in substantially unrotated dispositions. As a result, since the wheels of the system are connected to the two subchassis rather than the chassis, for the first time it is possible to design a vehicle wherein the wheels thereof remain in substantially zero camber dispositions under cornering conditions to maximize tire adhesion. Further, by mounting venturi ducts on the front and rear subchassis, the venturi ducts also remain level and do not sway during cornering, so that the ducts can be mounted closer to the roadway surface to provide greater efficiency without risk of engaging the roadway.
The closest prior art to the instant invention of which the applicant is aware is disclosed in the U.S. patents to Dickens, U.S. Pat. No. 3,831,965, Cunningham, Jr., U.S. Pat. No. 3,729,210, Melbar et al., U.S. Pat. No. 3,485,506, Bloise, U.S. Pat. No. 3,479,050, Corbin, U.S. Pat. Nos. 3,408,088 and 3,150,882, Guidobaldi, U.S. Pat. No. 2,791,440, and Freret, U.S. Pat. No. 2,260,102. However, while some of these references do teach chassis and suspensions wherein portions of the systems pivot about longitudinal axes in their respective vehicles, they do not teach a system wherein a chassis is resiliently pivotable about a longitudinal axis relative to front and rear subchassis and wherein the wheels of the system are independently movable. Hence, it is felt that all of the cited references are really of nothing more than general interest.
Accordingly, it is a primary object of the instant invention to provide a chassis and suspension system for a vehicle, whereby the wheels of the vehicle can be maintained in substantially perpendicular relation to a roadway surface during cornering conditions.
Another object of the instant invention is to provide a chassis and suspension system which provides enhanced vehicle handling under cornering conditions.
A further object of the instant invention is to provide a vehicle suspension system having a chassis and front and rear subchassis wherein the chassis is pivotally suspended from the front and rear subchassis and pivots about a substantially longitudinal axis which is above the longitudinal center of the gravity axis of the chassis.
A still further object of the instant invention is to provide a chassis and suspension system for a high speed vehicle wherein venturi ducts may be maintained in more closely spaced relation to a roadway surface without engaging same during cornering conditions.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.